Mechanical Gemstone Cleaning


quartz with inclusions - mechanical gemstone cleaning
Inclusions, some visible to the naked eye and others microscopic, are present in many gems. Some add great beauty and interest to a gemstone. However, they can also cause problems if you clean a gemstone in an appropriate manner. “Lodolite” (Quartz with inclusions) by Mario Cateb. Licensed under CC By 2.0.

The principal advantage of mechanical gemstone cleaning is getting beautiful results on difficult to clean set gems with minimal effort. You can purchase home kits for cleaning jewelry with ultrasonic, steam, and boiling systems. However, these techniques are best left to the professionals. (Hopefully, they have liability insurance to cover unfortunate outcomes).

The main risks mechanical gemstone cleaning poses to your jewelry doesn’t come from the equipment. Rather, they come from the unique internal characteristics of your individual gems. These include inclusions, undetected tiny fractures and structural stress, the gems’ chemical properties, and treatments received. If not identified by a professional gemologist beforehand, these qualities could lead to poor or disastrous results if you place your gemstones in the wrong kind of mechanical system.

Professional gemologists will understand the “internal personalities” of your gems. They can help you select the appropriate mechanical gemstone cleaning method.

The Risk Factors Hidden In Some Popular Gems

Emerald is a green colored beryl, normally a rather hardy mineral. However, heavy inclusions in an emerald can weaken its structure. The stresses of a mechanical cleaning could ruin, or even shatter, an emerald.

A topaz can appear perfectly flawless, even under magnification. However, to best present these gems, jewelry makers often press prong settings directly against a topaz’s cleavage plane. However, the gemstone has a natural tendency to break along this internal plane. If a prong exerts undue pressure on that plane, vibrations and even sudden temperature changes could split a topaz as neatly as a slice of bread.

topaz ring - mechanical gemstone cleaning
“Hug,” 14kt yellow and white gold ring set with a topaz stone and melee diamonds, by Mark Somma. Licensed under CC by 2.0.

Although a diamond may not cleave a readily as a topaz, the same danger lurks within it. In some incidents, one lovely diamond went into a mechanical cleaning system, but two or three smaller diamonds came out. Recent research suggests unseen liquid inclusions may have caused some of these accidents. The high temperatures created by some mechanical systems may cause the liquids to heat and then expand. Then … Crack!

How do mechanical gemstone cleaning systems work? The following brief descriptions of the three major systems will explain their operations and some caveats.

Ultrasonic Cleaning

Ultrasonic units usually consist of a stainless steel tank with millions of microscopic frequency waves bouncing around in a special liquid. The implosions (inward collapse) of the bubbles against a piece of jewelry placed inside the tank function as tiny vacuums. These siphon off dirt and grime.

9509342384_d3df1d3243_z
Ultrasonic units have many household uses. However, before you immerse your jewelry in one, know your gemstones and read about the ultrasonic cleaning system. “DSCF6331” by Emmanuel Gilloz. Licensed under CC By-SA 2.0.

The frequency impulses concentrate on the hardest element in the liquid. So, when you have a diamond in the bath, you can imagine where all the energy focuses. Should the diamond, or any other gemstone, have an incipient cleave or pressure point, the energy could aggravate the weakness to the point of destruction.

Avoid Cleaning These Gems Ultrasonically

Some gemstones, such as emeralds, rubies, and sapphires, receive oil treatments to enhance their color and transparency. The tiny bubbles in ultrasonic cleaning can drive out the oil. Unfortunately, this produces some very sad, sorry versions of your prized treasures in need of professional re-oiling.

Never submit opal, pearl, emerald, tanzanite, coral, turquoise, malachite, or amber to ultrasonic cleaning.

Unless a gemologist can assure you that your rubies or sapphires have never been oiled, keep these gems out of an ultrasonic tank, too.

Ultrasonic Cleaning Tips

Have your heart set on doing some ultrasonic cleaning at home? You can find a variety of units on Amazon or eBay. Here are some tips for using your cleaner:

  • Don’t let the jewelry piece lay on the bottom of the stainless steel tank. Keep it suspended so it floats in the liquid without touching the tank.
  • Check the temperature of the liquid. Prolonged use of an ultrasonic cleaner can run the temperature of the bath up to unsafe levels. This will expose your gems to thermal shock and can cause liquid-filled inclusions to blow the gem apart, literally.
  • Check the stones in your jewelry item before and after cleaning. The vibrations can dislodge a loose stone so that it falls to the bottom of the tank.
  • Use commercially prepared cleaning solutions intended for use in an ultrasonic cleaner.

Steam Cleaning and Boiling

Not too many consumers have a jewelry steam cleaner. Although more efficient for large scale cleaning tasks, they create some thermal dangers by elevating the temperature of a gemstone quickly then rapidly returning it to a normal temperature. Nonetheless, steam is highly efficient for melting grease and oil and blowing it away with other dirt. Fortunately, the average cleaning job just requires a quick squirt of high temperature steam.

Of the three major mechanical cleaning systems, boiling is the one most used by non-professionals. (Professionals often use it, too). It’s simple and can be done quickly, but it’s not without risk. Essentially, the boiling method is much like the warm water, mild detergent, and soft brush method, but at a much higher temperature. You place both jewelry and detergent in a pot of water and bring it to a boil. After a period of time, remove the pieces, then scrub them with a soft brush, rinse, and dry.

Steam Cleaning and Boiling Caveats

Just keep in mind that even a diamond can be ruined if the water boils off completely and it’s left sitting in a hot pot. (Diamonds can indeed burn).

The extreme temperatures and rapid changes that occur in steam cleaning and boiling are risky because some gemstones have inclusions that may actually be entirely different minerals. The two could have different heating coefficients. A rapid fluctuation in the host gem’s temperature could produce stresses that cause a split. Liquid inclusions, of course, can also create structural pressure if heated.

Herkimer diamonds/quartz - mechanical gemstone cleaning
Despite their name, Herkimer diamonds are actually doubly-terminated quartz crystals found in Herkimer, NY. These crystals contain inclusions of trapped, orangey mineralized water. “Quartz (Var: Herkimer Diamonds),” 2.9 x 2.1 x 1.6 cm, Ace of Diamonds Mine, Middleville, Town of Newport, Herkimer Co., New York, USA. © Rob Lavinsky, www.iRocks.com. Used with permission.

Steam Cleaning and Boiling Tips

If ever you intend to expose one of your gems to high heat, prepare the gem first. Pre-warm it by immersing it first in warm, then warmer water. (All three mechanical cleaning techniques have the potential to elevate a stone’s temperature too quickly). If you make it to a high temperature safely, realize that coming back down again poses an equal challenge. Cool it down, this time by placing it in warm water. Avoid exposing a gem you’ve just heated to cold air.

The Bottom Line

Even if you want to leave mechanical gemstone cleaning to the professionals, ask them questions about their procedures and your gemstones. If their answers don’t satisfy you, go elsewhere. A little knowledge of gems, their care requirements, and different cleaning systems will help you make the best possible choice.

Gemstone Care Series

About the author
Dr. Gerald Wykoff GG CSM
Dr. Gerald Wykoff is GG (Graduate Gemologist), a CSM (Certified Supreme Master gemcutter), educator, and author of several gemology books. He founded the American Society of Gemcutters in the 1980s and served for more than 10 years as the editor of its monthly magazine, American Gemcutter.
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